1. Field of the Invention
The present invention relates to thermal-release double-coated pressure-sensitive adhesive tapes or sheets, and methods of processing adherends using them.
2. Description of the Related Art
There have been known thermal-release pressure-sensitive adhesive tapes or sheets which include a substrate (carrier), and a pressure-sensitive adhesive layer containing a foaming agent such as heat-expandable microspheres (heat-expandable pressure-sensitive adhesive layer), and being arranged on the substrate (e.g., Japanese Unexamined Patent Application Publication (JP-A) No. S56-61468). Such thermal-release pressure-sensitive adhesive tapes or sheets are configured to make it possible to easily separate an article as an adherend easily after accomplishment of the purpose of bonding of the article. This is achieved in the following manner. The heat-expandable pressure-sensitive adhesive layer is heated to foam or expand, whereby the heat-expandable pressure-sensitive adhesive layer has an uneven surface to have a smaller adhesion area with the adherend and to have a reduced adhesive strength (adhesive force). Thus, the adherend can be easily separated from the tape or sheet. These thermal-release pressure-sensitive adhesive tapes or sheets are therefore widely used in purposes of every kind. They are used, for example, for fixing electronic components or materials thereof during processing, or for carrying out physical distribution such as transportation.
For example, the thermal-release pressure-sensitive adhesive tapes or sheets may be a double-coated type thermal-release pressure-sensitive adhesive tape or sheet (thermal-release double-coated pressure-sensitive adhesive tape or sheet). The tapes or sheets include a substrate, a pressure-sensitive adhesive layer containing a foaming agent (foaming agent-containing pressure-sensitive adhesive layer), arranged on one side of the substrate, and a pressure-sensitive adhesive layer containing no foaming agent (foaming agent-free pressure-sensitive adhesive layer), arranged on the other side of the substrate. The thermal-release double-coated pressure-sensitive adhesive tape or sheet is generally used in the following manner. An article to be processed is affixed to the surface of the foaming agent-containing pressure-sensitive adhesive layer serving as a thermal-release pressure-sensitive adhesive layer; and the foaming agent-free pressure-sensitive adhesive layer not serving as a thermal-release pressure-sensitive adhesive layer is affixed to the surface of a pedestal. After processing the article affixed to the pedestal through the tape or sheet, the processed article is released from the thermal-release double-coated pressure-sensitive adhesive tape or sheet by heating, and the thermal-release double-coated pressure-sensitive adhesive tape or sheet is then removed from the pedestal. In this case, the pedestal released from the thermal-release double-coated pressure-sensitive adhesive tape or sheet is reusable.